There are many applications where there exists a need for transforming a linear movement or force into a rotational movement or torque and/or vice versa. Examples of such applications are energy generation devices such as wave and wind power generators and different industrial lifting or actuation systems. For the purpose of transformation between linear and rotational motion in such systems, different types of gear arrangements may be utilized. The gear arrangements typically comprise a linearly movable, possibly reciprocal, member which, e.g. by means of meshing cogs, co-acts with a rotational member. Such arrangements are generally referred to as rack and pinion drives. When it is desirable to achieve a certain gear ratio between the input motion or force and the output motion or torque the gear arrangement may comprise additional cog wheels or gears meshing with the pinion and arranged between the rack and the output or input shaft.
The present invention may be used at various applications of the above mentioned type and also in others. An application of certain interest is the wave power generation industry. WO 2012/008896 A1 discloses an energy transforming system which may be utilized for converting ocean wave energy into electrical power. According to one embodiment, the system comprises an oscillator with two cylinder-piston arrangements arranged vertically face to face. The cylinders contain a fluid, and the two pistons are mechanically connected to each other by means of a rod. A buoy which is influenced by ocean waves is connected to the piston of one of the cylinders and causes a reciprocal oscillating movement of the rod when affected by the ocean waves.
For converting the kinetic energy of the rod into electrical power, a gear arrangement may be arranged between the reciprocal rod and rotating electrical generator or alternator.
At these types of gear arrangements it is of vital interest that the entire arrangement is durable and has a long and predictable service life. A further important aspect is that the inertia of the moving parts should be as low as possible, thus that the weight of e.g. the cog wheels and shafts should be as low as possible. Correspondingly, it is also most desirable that the dimensions of the gear arrangement and its constituent parts are kept as small as possible. On the other hand, it is also important that the entire arrangement should be able to sustain high and varying loads, since the loads from ocean waves and actuation loads in industrial machinery may vary largely. It is thus of great importance that the gear arrangement may be designed with a high load to volume-weight ratio.